Question 621465
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
Note:  Bell shaped Curve showing placement of z = 0, z = ±1, 2, 3 
Left or Right of z = 0 being 50% of the area under the standard normal curve...
The area under a normal curve = 1
{{{drawing(400,200,-5,5,-.5,1.5, graph(400,200,-5,5,-.5,1.5, exp(-x^2/2)), green(line(1,0,1,exp(-1^2/2)),line(-1,0,-1,exp(-1^2/2))),green(line(2,0,2,exp(-2^2/2)),line(-2,0,-2,exp(-2^2/2))),green(line(3,0,3,exp(-3^2/2)),line(-3,0,-3,exp(-3^2/2))),green(line( 0,0, 0,exp(0^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z))}}}
As to: A set of data is normally distributed with a mean of 85 and SD of 4.59 
x = 90 
 z = (90-85)/4.59 = 1.089  
Exel function NORMSDIST(1.089) = .862 , 86.2% to the left and 13.8% to the right
{{{drawing(400,200,-5,5,-.5,1.5, graph(400,200,-5,5,-.5,1.5, 0,exp(-x^2/2)), blue(line( 1.089,0, 1.089,exp(-1.089^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z))}}}
As:a normal distribution with mu = 25 and sigma = 9, if z = -2, 
then z = (x -25)/9 = -2,   and   x =  -18 + 25 = 7